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Journal ArticleDOI

Preparation and photoionization potentials of molecules of sodium, potassium, and mixed atoms

01 Mar 1978-Journal of Chemical Physics (AIP Publishing)-Vol. 68, Iss: 5, pp 2327-2336
TL;DR: In this article, photoionization near the threshold allows identification of Naxx?16, Kxx?12, and NaxKyx+y?6, which is the longest contiguous series of any property as a function of cluster size.
Abstract: In supersonic nozzle beams of sodium, potassium, and Na/K molecular aggregates Mx have been investigated by several techniques based on mass spectrometry. By electron impact ionization with energy of 20 eV clusters with x≳4 are not observable. Photoionization near the threshold allows identification of Naxx?16, Kxx?12, and NaxKyx+y?6. Single photon ionization thresholds for Naxx?14 are given, this being the hitherto longest contiguous series of any property as a function of cluster size. For Kxx?8 and for 8 Na/K mixed clusters PI thresholds are similarly determined. Very accurate two photon photoionization thresholds for Na2 and K2 have been obtained. Theoretical models of metal clusters from recent publications are not able to adequately interpret the electronic properties of these particles as reflected by the ionization potentials.
Citations
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Journal ArticleDOI
TL;DR: In this paper, cold beams of metal clusters are produced by combining a laser vaporization technique with pulsed supersonic nozzle technology, and the results show that the resulting cold beams are more stable than those of traditional laser-based methods.
Abstract: Cold beams of metal clusters are produced by combining a laser vaporization technique with pulsed supersonic nozzle technology. (AIP)

750 citations

Journal ArticleDOI
TL;DR: The field of cluster research can trace its origins back to the mid-nineteenth century when early studies of colloids, aerosols, and nucleation phenomena were reported.
Abstract: The field of cluster research can trace its origins back to the mid-nineteenth century when early studies of colloids, aerosols, and nucleation phenomena were reported. The field underwent a resurgence of interest several decades ago when well-defined clusters were observed in supersonic expansions that could be investigated using mass spectrometers. The advent of the laser provided a new dimension, enabling detailed spectroscopic observations through the probing of systems of varying size and degree of solvation. Modern interest derives from recognition that interrogating clusters provides a way of studying the energetics and dynamics of intermediate states of matter as cluster systems evolve from the gas toward the condensed state. Herein, we endeavor to highlight some of the significant advances which have been made during the past several decades that have led to a nearly explosive growth of interest in the field of cluster science. Finally, we conclude that the field will continue to expand through i...

631 citations

Journal ArticleDOI
TL;DR: A review of core-level binding energy shifts observed in photoelectron spectroscopy can be found in this paper, where the authors focus on shifts since most of the chemical and physical insights provided by core levels are derived not from the core energies themselves but from shifts they exhibit.

588 citations

Book ChapterDOI
TL;DR: An overview of quasiparticle calculations in solids, and particular, the GW approximation (GWA), can be found in this paper, where the authors present parallel algorithms both for reciprocal and real-space/imaginary-time GWA calculations and several alternative methods to determine excited states of solids within density functional theory.
Abstract: This chapter provides an overview of quasiparticle calculations in solids, and, in particular, the GW approximation (GWA). A successful approximation for the determination of excited states of solids is based on the quasiparticle concept and the Green function method. The Coulomb repulsion between electrons leads to a depletion of negative charge around a given electron, and the ensemble of this electron and its surrounding positive screening charge forms a quasiparticle. The mathematical description of quasiparticles is based on the single-particle Green function (G), whose exact determination requires complete knowledge of the quasiparticle self-energy ∑. The self-energy ∑ is a non-Hermitian, energy-dependent, nonlocal operator that describes exchange and correlation effects beyond the Hartree approximation. A determination of the self-energy can only be approximate, and a working scheme for the quantitative calculation of excitation energies in metals, semiconductors, and insulators is the so-called dynamically screened interaction or the GWA. The chapter also discusses (1) the physics and extensions of the GWA; (2) numerical aspects of GWA calculations; (3) applications of the GWA to semiconductors, insulators and metals; and (4) the relevance of GWA calculations to optical response. Finally, the chapter presents parallel algorithms both for reciprocal and real-space/imaginary-time GWA calculations and several alternative methods to determine excited states of solids within density functional theory.

577 citations

Journal ArticleDOI
TL;DR: In this article, a combined experimental and theoretical study of small gold cluster anions is performed, where the experimental effort consists of ion mobility measurements that lead to the assignment of the collision cross sections for the different cluster sizes at room temperature and the theoretical study is based on abomolecular dynamics calculations with the goal to find energetically favorable candidate structures.
Abstract: A combined experimental and theoretical study of small gold cluster anions is performed. The experimental effort consists of ion mobilitymeasurements that lead to the assignment of the collision cross sections for the different cluster sizes at room temperature. The theoretical study is based on ab initiomolecular dynamics calculations with the goal to find energetically favorable candidate structures. By comparison of the theoretical results with the measured collision cross sections as well as vertical detachment energies (VDEs) from the literature, we assign structures for the small Au n − ions (n<13) and locate the transition from planar to three-dimensional structures. While a unique assignment based on the observed VDEs alone is generally not possible, the collision cross sections provide a direct and rather sensitive measure of the cluster structure. In contrast to what was expected from other metal clusters and previous theoretical studies, the structural transition occurs at an unusually large cluster size of twelve atoms.

506 citations

References
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Journal ArticleDOI

23,110 citations

Journal ArticleDOI
TL;DR: In this paper, Fock's Naherungsmethode zur Behandung des quantenmechanischen Mehrelektronenproblems aufgestellten Gleichungen werden auf etwas allgemeinerer Grundlage diskutiert.

5,844 citations

Book
01 Jan 1950

5,027 citations

Journal ArticleDOI
TL;DR: In this article, the melting points of small gold particles have been measured using a scanning electron-diffraction technique and the experimental results are quantitatively in good agreement with two phenomenological models.
Abstract: Recently, small particles have been shown to exhibit a melting temperature which depends on the particle size. The various possible experimental methods have been compared and measurements of the melting points of small gold particles have been made using a scanning electron-diffraction technique. This method was applied to particles having diameters down to 20 \AA{}. Consideration of the size distribution over an entire sample makes it necessary to carry out a careful analysis of the experimental results in order to deduce the melting temperature of particles having a well-defined diameter. The experimental results are quantitatively in good agreement with two phenomenological models. The first model describes the equilibrium condition for a system formed by a solid particle, a liquid particle having the same mass, and their saturating vapor phase. The second model assumes the preexistence of a liquid layer surrounding the solid particle and describes the equilibrium of such a system in the presence of the vapor phase. In order to permit a better comparison between both models, a new expression for the thermodynamic equilibrium condition has been derived in the present work. In the case of the first model, the agreement was obtained using only the physical constants of massive gold. In applying the second model, however, one is compelled to assume the existence of a liquid layer having a thickness of about 6 \AA{}.

3,074 citations

01 Jan 1976
TL;DR: In this paper, the Hartree-Fock Approximation of many-body techniques and the Electron Gas Polarons and Electron-phonon Interaction are discussed.
Abstract: Mathematical Introduction Acoustic Phonons Plasmons, Optical Phonons, and Polarization Waves Magnons Fermion Fields and the Hartree-Fock Approximation Many-body Techniques and the Electron Gas Polarons and the Electron-phonon Interaction Superconductivity Bloch Functions - General Properties Brillouin Zones and Crystal Symmetry Dynamics of Electrons in a Magnetic Field: de Haas-van Alphen Effect and Cyclotron Resonance Magnetoresistance Calculation of Energy Bands and Fermi Surfaces Semiconductor Crystals I: Energy Bands, Cyclotron Resonance, and Impurity States Semiconductor Crystals II: Optical Absorption and Excitons Electrodynamics of Metals Acoustic Attenuation in Metals Theory of Alloys Correlation Functions and Neutron Diffraction by Crystals Recoilless Emission Green's Functions - Application to Solid State Physics Appendix: Perturbation Theory and the Electron Gas Index.

1,588 citations